Mortising machines have been used for many years to form holes, grooves, or slots into or through posts or other workpieces. In a typical situation, a mortise, in the form of a rectangular cavity, is cut into a piece of timber or other material which is to receive a tenon. Mortising machines often use a chainsaw type blade for cutting rectangular mortises in fairly large posts. A variety of brackets and devices have been used to hold such a workpiece while the mortise is formed by the mortising machine. These devices have proven difficult to use for holding larger posts or logs, especially rounded posts or logs, while the mortise is being formed.
Some mortise machines have been designed to clamp on to the outer edges of square posts while a mortise is cut but this becomes much more difficult with round logs or posts. When round logs are used, mortises have sometimes been formed by simply drilling holes into the rounded post and then removing the remaining material between the holes with the aid of a hand chisel. This process, however, is time consuming and leaves a poorly formed mortise for receiving a tenon.
Another problem with many of the prior art devices is that the workpiece must be removed and repositioned before the opposite side of the workpiece can be operated on by the mortising machine. For instance, Koster, U.S. Pat. No. 1,015,497, issued Jan. 23, 1912, shows a device for holding a workpiece in which a hole is bored from one direction only. Also, the Koster device is used to hold relatively small workpieces such as chair legs or table legs. The device is not designed to hold a larger post which is subjected to a chainsaw type mortising machine.
A mortising machine, using a chain cutter and a clamping device, is disclosed in Downing, U.S. Pat. No. 112,228, issued Feb. 28, 1871. However, here the device is designed primarily for holding square workpieces. Additionally, the mortise can be formed from only one side of the workpiece unless the workpiece is removed from the device and repositioned.
In Jesson et al., U.S. Pat. No. 410,975, issued Sep. 10, 1889, a device is disclosed which holds rounded workpieces while a mortise is formed. However, once again the rounded workpieces are relatively small umbrella handles and the mortise can only be formed on one side of the umbrella handle without removing the handle from the device.
A device for holding larger posts in which mortises are formed is disclosed in Rahmel, U.S. Pat. No. 1,186,682, issued Jun. 13, 1916. Once again, the Rahmel device is designed to securely hold square posts while the mortise is formed with, for example, a chainsaw mortiser. This device is designed so that the workpiece may quickly be clamped and unclamped allowing it to be moved along a table while mortises are formed at various points along one side of the post. However, a mortise can not be formed from opposite sides of the post without removing the post from the clamping device.
Other similar devices are also shown in the prior art. An endless chain mortising machine is disclosed in Daniels, U.S. Pat. No. 268,003, issued Nov. 28, 1882. Another mortising machine is shown in Kraus, U.S. Pat. No. 306,404, issued Oct. 14, 1884.
The present invention addresses the foregoing drawbacks of known devices.